Stalk rot infection in corn reduces the efficiency of carbohydrate transport from the stalk up to the ears during grainfill, which reduces crop yield. A corn plant will die altogether if infection advances to the point that the pith pulls away from the outer rind of the stalk, which can eventually result in a stalk consisting of little more than a hollow tube that is no longer able transport water and nutrients to the rest of the plant. Furthermore, a stalk weakened by infection is more likely to collapse at one or more points along its length (lodging), which typically results in a plant that yields no harvestable grain. Stalk rots typically reduce yields up to 5% in almost any field where corn is cultivated. In years with particularly bad infection rates, yield losses reach 10-20%, and in some locations when infection is particularly acute, 100% yield loss can occur.
Bacterial Stalk Rot (BSR) is a form of stalk rot caused by several species of bacteria. BSR infection is characterized by discoloration of leaf sheath and stalk followed by lesions on the leaves and sheath that progresses as the plant matures. Eventually the stalk rots completely resulting in weak, spongy stalks that are prone to lodging. Due to the lack of chemical controls for BSR, growers are faced with limited options for managing the disease. Since the most effective approach is to select hybrids that are intrinsically resistant, what is needed are methods of identifying genetic sources of BSR resistance and more effective methods of introgressing those genetic elements into commercial lines to provide new hybrids with improved genetic resistance to BSR infection.